Multidrug Resistance and Virulence Profiles of <i>Salmonella</i> Isolated from Swine Lymph Nodes

Abstract

<i>Salmonella</i> spp. is a foodborne pathogen present in the pork production chain, leading to potential contamination of end products and causing salmonellosis cases and outbreaks worldwide. The emergence of multidrug-resistant (MDR) <i>Salmonella</i> spp., especially isolates obtained from animal origin food, is a global concern. This study aimed to isolate <i>Salmonella</i> from swine mesenteric lymph nodes (MLN) and to characterize the virulence and antibiotic resistance profiles. MLN samples were obtained from a swine slaughterhouse and subjected to <i>Salmonella</i> spp. isolation. Ten MLN samples were positive and 29 isolates were identified based on PCR (<i>invA</i> and <i>ompC</i>) and serotyping: Derby, Cerro, and Give. Pulsed-field gel electrophoresis allowed to group the isolates based on their serotypes, resulting in three major clusters. All isolates presented the virulence-related genes <i>pefA</i>, <i>sipA</i>, <i>sopB</i>, <i>spaN</i>, and <i>pagC</i>. Relatively high numbers of <i>Salmonella</i> spp. were resistant to neomycin, polymyxin B, ciprofloxacin, tetracycline, and nalidixic acid. Furthermore, 25 isolates presented simultaneous resistance to three or more antibiotic classes, being characterized as MDR. The obtained results confirmed the relevance of swine as reservoirs of <i>Salmonella</i> spp. in the pork production chain and demonstrated the MDR profiles of isolates. Proper control and surveillance are required to avoid the contamination of end products.